Bibcode
Delgado Mena, E.; Moya, A.; Adibekyan, V.; Tsantaki, M.; González Hernández, J. I.; Israelian, G.; Davies, G. R.; Chaplin, W. J.; Sousa, S. G.; Ferreira, A. C. S.; Santos, N. C.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 624, id.A78, 24 pp.
Fecha de publicación:
4
2019
Revista
Número de citas
115
Número de citas referidas
105
Descripción
Aims: The purpose of this work is to evaluate how several
elements produced by different nucleosynthesis processes behave with
stellar age and provide empirical relations to derive stellar ages from
chemical abundances. Methods: We derived different sets of ages
using Padova and Yonsei-Yale isochrones and HIPPARCOS and Gaia
parallaxes for a sample of more than 1000 FGK dwarf stars for which he
have high-resolution (R 115 000) and high-quality spectra from the
HARPS-GTO program. We analyzed the temporal evolution of different
abundance ratios to find the best chemical clocks. We applied
multivariable linear regressions to our sample of stars with a small
uncertainty on age to obtain empirical relations of age as a function of
stellar parameters and different chemical clocks. Results: We
find that [α/Fe] ratio (average of Mg, Si, and Ti), [O/Fe] and
[Zn/Fe] are good age proxies with a lower dispersion than the
age-metallicity dispersion. Several abundance ratios present a
significant correlation with age for chemically separated thin disk
stars (i.e., low-α) but in the case of the chemically defined
thick disk stars (i.e., high-α) only the elements Mg, Si, Ca, and
Ti II show a clear correlation with age. We find that the thick disk
stars are more enriched in light-s elements than thin disk stars of
similar age. The maximum enrichment of s-process elements in the thin
disk occurs in the youngest stars which in turn have solar metallicity.
The slopes of the [X/Fe]-age relations are quite constant for O, Mg, Si,
Ti, Zn, Sr, and Eu regardless of the metallicity. However, this is not
the case for Al, Ca, Cu and most of the s-process elements, which
display very different trends depending on the metallicity. This
demonstrates the limitations of using simple linear relations based on
certain abundance ratios to obtain ages for stars of different
metallicities. Finally, we show that by using 3D relations with a
chemical clock and two stellar parameters (either Teff,
[Fe/H] or stellar mass) we can explain up to 89% of age variance in a
star. A similar result is obtained when using 2D relations with a
chemical clock and one stellar parameter, explaining up to a 87% of the
variance. Conclusions: The complete understanding of how the
chemical elements were produced and evolved in the Galaxy requires the
knowledge of stellar ages and precise chemical abundances. We show how
the temporal evolution of some chemical species change with metallicity,
with remarkable variations at super-solar metallicities, which will help
to better constrain the yields of different nucleosynthesis processes
along the history of the Galaxy.
Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A78Based
on observations collected at the La Silla Observatory, ESO (Chile), with
the HARPS spectrograph at the 3.6 m ESO telescope (ESO runs ID
72.C-0488, 082.C-0212, and 085.C-0063).
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Garik
Israelian